EP0594070A1 - Rauschunterdrückung in einem Datenerfassungssystem mit Speicherleuchtstoff - Google Patents

Rauschunterdrückung in einem Datenerfassungssystem mit Speicherleuchtstoff Download PDF

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Publication number
EP0594070A1
EP0594070A1 EP93116675A EP93116675A EP0594070A1 EP 0594070 A1 EP0594070 A1 EP 0594070A1 EP 93116675 A EP93116675 A EP 93116675A EP 93116675 A EP93116675 A EP 93116675A EP 0594070 A1 EP0594070 A1 EP 0594070A1
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EP
European Patent Office
Prior art keywords
digital
signal
reference signal
laser
image
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EP93116675A
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English (en)
French (fr)
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EP0594070B1 (de
Inventor
Sreeram C/O Eastman Kodak Company Dhurjaty
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Eastman Kodak Co
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Eastman Kodak Co
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits

Definitions

  • This invention relates in general to laser imaging systems and, more particularly, to storage phosphor systems in which data acquired from a storage phosphor by laser scanning is corrected for laser noise.
  • a storage phosphor is exposed to an x-ray image of an object to record a latent image in the storage phosphor.
  • the latent x-ray image is read out by stimulating the storage phosphor with a relatively long wavelength simulating radiation, such as red or infrared light.
  • a relatively long wavelength simulating radiation such as red or infrared light.
  • the storage phosphor releases emitted radiation of an intermediate wavelength, such as blue light, in proportion to the quantity of x-rays that were received.
  • the storage phosphor is scanned in a raster pattern by a laser beam deflected by an oscillating or rotating scanning mirror.
  • the emitted radiation from the storage phosphor is collected by a light collector and detected by a photodetector, such as a photomultiplier to produce an electronic image signal.
  • a photodetector such as a photomultiplier
  • the storage phosphor is translated in a page scan direction past a laser beam, that is repeatedly deflected in a line scan direction perpendicular to the motion of storage phosphor to form a scanning raster.
  • a radiation image information readout apparatus reads out a stimulable phosphor in which a radiation image is recorded by use of stimulating rays impinging thereon.
  • the gain of the readout system is controlled, according to a fluctuation of the intensity of the stimulating ray source, by use of an additional photodetector, which detects the laser intensity before the stimulable phosphor is scanned.
  • a similar system is disclosed in U.S. Patent No. 4,150,402, in which the effect of laser noise in a scanning laser read system is reduced by sampling the laser beam prior to scanning a document.
  • the sampled laser beam is converted to an electrical signal which is amplified and applied to a gain control device, such that noise present in the output laser beam modulates the signal detected from scanning the document to eliminate laser noise.
  • U.S. Patent No. 4,896,222 Another proposal to reduce laser generated noise in a storage phosphor system is disclosed in U.S. Patent No. 4,896,222.
  • an object such as a stimulable phosphor sheet, on which image information is recorded, is scanned by a laser beam, and emitted light is photoelectrically detected to produce an image signal representing the image formation.
  • a monitor signal representing the light beam is detected by a photodetector and is divided into a high frequency component and a low frequency component.
  • a corrective signal is produced by multiplying a ratio of the high frequency component to the low frequency component by a constant. This corrective signal is then subtracted from the image signal.
  • U.S. Patent 4,977,322 discloses a technique to minimize image signal noise in a stimulable phosphor system. As disclosed, a detected image signal is fed to a high frequency component decreasing device for decreasing the high frequency component, the level of the image signal is detected, and the high frequency component of the image signal is decreased by the high frequency component decreasing device, in accordance with a decrease in the level of the image signal.
  • a laser noise correction apparatus comprises: a first photodetector for detecting the scanned image and for producing an image signal; a second photodetector for detecting the laser output beam, and for producing a reference signal, wherein the image signal and the reference signal contain a laser noise part; first analog-to-digital converter means for converting said image signal to a digital image signal; means for subtracting a predetermined non-varying part of the laser signal from the reference signal to produce a residue reference signal representative of laser noise; means for amplifying the residue reference signal by a factor N; second analog-to-digital converter means for converting the residue reference signal to a digital residue reference signal; means for dividing the digital residue reference signal by said factor N; means for combining the divided digital residue reference signal with a digital
  • storage phosphor laser imaging system 10 includes a laser 12, such as a helium neon gas laser, for stimulating a storage phosphor screen 14.
  • Laser 12 produces a laser beam 16, which passes through a shutter 18, which is open during a storage phosphor reading operation and closed at other times.
  • the laser beam 16 is reflected by mirror 20 through beam splitter 22, which directs a portion of the laser beam 16 to reference photodetector 24.
  • laser beam 16 passes through collimator 26.
  • the collimated beam is deflected by an oscillating mirror 28 driven by galvanometer motor 30, which provides a raster motion of the laser beam 16.
  • An F-THETA lens 32 produces a flat field of focus and constant linear velocity at the plane of storage phosphor 14.
  • the laser beam is reflected by folding mirror 34, which directs the beam through light collector 36 onto storage phosphor 14.
  • the stimulating laser beam causes storage phosphor 14 to emit light which is collected by light collector 36 which directs the emitted light onto photomultiplier (PMT) 38.
  • a filter 40 in front of PMT 38 blocks scattered laser light and passes emitted light to PMT 38.
  • a cassette 15 containing a storage phosphor 14 is placed on cassette load platform 42 and the load lever 43 is rotated to clamp the storage phosphor cassette 15 in place.
  • a storage phosphor extraction mechanism (not shown) extracts the storage phosphor 14 from the cassette 15 onto translation stage 44.
  • Translation stage 44 is driven by a mechanism 46 actuated by stepper motor 48.
  • the translation stage 44 is moved in a direction perpendicular to the loading direction to a point under collector 36, at which point data acquisition begins through stimulation by laser beam 16.
  • a raster scan is produced of the latent image stored in storage phosphor 14.
  • the PMT 38 and galvo motor 30 are turned off, and translation stage 44 is returned to a home position opposite cassette load platform 42.
  • erase lamp 50 driven by erase power supply 52, is turned on to erase storage phosphor 14. Following a predetermined erase period, erase lamp 50 is turned off, and the storage phosphor screen extraction mechanism returns storage phosphor 14 to cassette 15. The load lever 44 is then rotated to unlock cassette 15 for removal.
  • the image signal from PMT 38 and reference signal from reference photodetector 24 are sent to image acquisition circuit 54, which will be described in detail with reference to FIG. 2.
  • the image signal is applied to a variable gain transconductance amplifier 56, which transforms the current signal from PMT 38 into a voltage signal.
  • the gain of amplifier 56 can be varied under computer control in order to accommodate varying storage screen sizes as well as varying scanning speeds.
  • the voltage from amplifier 56 is input to the Bessel filter 58.
  • Filter 58 is an anti-aliasing filter (typically a 4-pole low-pass filter) with Bessel response, in order to maintain the shape of the signal input from amplifier 56. Filter 58 also effects a slight time delay of the image signal from amplifier 56.
  • ADC 60 analog-to-digital converter
  • ADC 60 may, for example, be a 16 bit flash converter.
  • LUT log lookup table
  • a correction signal is subtracted from the image signal to produce a corrected image signal.
  • the correction signal is derived from the laser reference signal from photodetector 24, which is amplified by amplifier 64.
  • Amplifier 64 converts the reference current signal from photodetector 24 into a reference voltage signal, which is applied to the non-inverting input of comparator 66.
  • Comparator 66 also receives a bias signal representing the known non-varying portion of the reference signal voltage.
  • the bias reference signal is stored as a digital signal in bias reference register 68.
  • Register 68 supplies a digital signal to bias DAC 70, which produces the analog bias reference voltage applied to comparator 66.
  • laser noise is approximately 1% of the total laser reference signal. Therefore, DAC 70 produces the non-varying reference bias voltage, which represents 99% of the laser intensity.
  • This bias voltage is subtracted from the reference signal, and comparator 66 produces a residue reference signal, which represents the laser noise.
  • the residue reference signal is passed through a Bessel filter 72, which has the same characteristics as Bessel filter 58 in the image signal channel. Thus, time delays of the reference and the image signal are equalized before digitization. Bessel filter 72 can also be located before comparator 66 to achieve the same equalization.
  • ADC 76 is triggered by the same trigger signal as ADC 60.
  • the signal from ADC 76 is divided by a factor N by divider circuit 78. Division is effected by shifting the signal to the right by M places.
  • the digital residue reference signal is then added in adder 80 with the bias reference signal (which represents the non varying part of the laser reference signal) from bias reference register 68 to generate, for example, a 13 bit reference signal representing the laser intensity.
  • the signal from adder 80 is linear and is converted to a log digital error signal by log LUT 82, which produces, for example, a 9 bit log correction signal.
  • Adder 84 combines the 12 bit log image signal and 9 bit log correction signal to produce a 12 bit log corrected image signal.
  • the present invention has industrial application in laser imaging systems (such as storage phosphor laser imaging systems, and has the following advantages:

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Facsimile Scanning Arrangements (AREA)
  • Radiography Using Non-Light Waves (AREA)
  • Facsimile Image Signal Circuits (AREA)
EP93116675A 1992-10-23 1993-10-15 Rauschunterdrückung in einem Datenerfassungssystem mit Speicherleuchtstoff Expired - Lifetime EP0594070B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US965657 1992-10-23
US07/965,657 US5260561A (en) 1992-10-23 1992-10-23 Noise reduction in a storage phosphor data acquisition system

Publications (2)

Publication Number Publication Date
EP0594070A1 true EP0594070A1 (de) 1994-04-27
EP0594070B1 EP0594070B1 (de) 1997-08-27

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EP93116675A Expired - Lifetime EP0594070B1 (de) 1992-10-23 1993-10-15 Rauschunterdrückung in einem Datenerfassungssystem mit Speicherleuchtstoff

Country Status (4)

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US (1) US5260561A (de)
EP (1) EP0594070B1 (de)
JP (1) JP3359713B2 (de)
DE (1) DE69313396T2 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999039503A1 (de) * 1998-01-30 1999-08-05 Christof Steiner Verfahren und anordnung zum auslesen von auf einer bildplatte gespeicherter strahlungsbildinformation

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6444971B1 (en) * 1999-12-31 2002-09-03 Leica Microsystems Heidelberg Gmbh Method and system for compensating intensity fluctuations of an illumination system in a confocal microscope
US6492655B2 (en) * 2000-04-05 2002-12-10 Fuji Photo Film Co., Ltd. Method and apparatus for reading image information
CN103418911A (zh) * 2012-05-21 2013-12-04 武汉金至园科技有限公司 窄小空间激光打标方法及其打标机

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63186387A (ja) * 1987-01-29 1988-08-01 Hitachi Ltd ２値化回路
US4896222A (en) * 1987-09-07 1990-01-23 Fuji Photo Film Co., Ltd. Method of and apparatus for correcting image signal
WO1991018470A1 (en) * 1990-05-11 1991-11-28 Eastman Kodak Company Method and apparatus for compensating for sensitivity variations in the output of a solid state image sensor

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USRE31847E (en) * 1973-01-02 1985-03-12 Eastman Kodak Company Apparatus and method for producing images corresponding to patterns of high energy radiation
US4150402A (en) * 1977-04-07 1979-04-17 Xerox Corporation Method and apparatus for reducing the effect of laser noise in a scanning laser read system
JPS5719700A (en) * 1980-07-10 1982-02-01 Fuji Photo Film Co Ltd Radiation image information reading gain controller
JPS6087565A (ja) * 1983-10-19 1985-05-17 Fuji Photo Film Co Ltd 画像走査読取方法
US4922100A (en) * 1985-03-13 1990-05-01 Konishiroku Photo Industry Co., Ltd. Method for reading a radiographic image
US4977322A (en) * 1986-03-28 1990-12-11 Fuji Photo Film Co., Ltd. Method and apparatus for minimizing image signal noise, and radiation image read-out method and apparatus
JPS62245777A (ja) * 1986-04-17 1987-10-27 Fuji Photo Film Co Ltd 放射線画像情報読取装置
US4861994A (en) * 1986-06-17 1989-08-29 Fuji Photo Film Co., Ltd. Method of measuring after-glow of stimulable phosphor sheet, and method of adjusting radiation image read-out conditions
US4743759A (en) * 1986-10-14 1988-05-10 Eastman Kodak Company Light collector for photo-stimulable phosphor imaging system
JP2805303B2 (ja) * 1987-06-10 1998-09-30 富士写真フイルム株式会社 画像情報読取装置におけるシェーディング補正方法
JPS6486130A (en) * 1987-09-28 1989-03-30 Fuji Photo Film Co Ltd Image signal correcting method

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63186387A (ja) * 1987-01-29 1988-08-01 Hitachi Ltd ２値化回路
US4896222A (en) * 1987-09-07 1990-01-23 Fuji Photo Film Co., Ltd. Method of and apparatus for correcting image signal
WO1991018470A1 (en) * 1990-05-11 1991-11-28 Eastman Kodak Company Method and apparatus for compensating for sensitivity variations in the output of a solid state image sensor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 12, no. 468 (P - 797) 8 December 1988 (1988-12-08) *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999039503A1 (de) * 1998-01-30 1999-08-05 Christof Steiner Verfahren und anordnung zum auslesen von auf einer bildplatte gespeicherter strahlungsbildinformation
US6518564B1 (en) * 1998-01-30 2003-02-11 Christof Steiner Process and device for reading radiation image information stored on an image medium by detecting both the luminescent light emitted and the reflected read out light

Also Published As

Publication number Publication date
JP3359713B2 (ja) 2002-12-24
US5260561A (en) 1993-11-09
JPH06205215A (ja) 1994-07-22
DE69313396D1 (de) 1997-10-02
DE69313396T2 (de) 1998-03-05
EP0594070B1 (de) 1997-08-27

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